<!------------------------------------------------------------
  文件名:   ch3-2.html
  第三章:   directive 用法
  开发平台: VSCode 1.39.1
  Vue 实战小慕读书中后台 By Sam
------------------------------------------------------------->
<html>
  <head>
    <title>directive 用法</title>
    <script src="https://cdn.jsdelivr.net/npm/vue/dist/vue.js"></script>
  </head>
  <body>
    <div id="root">
      <div v-loading="isLoading">{{data}}</div>
      <button @click="update">更新</button>
    </div>
    <script>
      Vue.directive('loading', {
        update(el, binding, vnode) {
          if (binding.value) {
            const div = document.createElement('div')
            div.innerText = '加载中...'
            div.setAttribute('id', 'loading')
            div.style.position = 'absolute'
            div.style.left = 0
            div.style.top = 0
            div.style.width = '100%'
            div.style.height = '100%'
            div.style.display = 'flex'
            div.style.justifyContent = 'center'
            div.style.alignItems = 'center'
            div.style.color = 'white'
            div.style.background = 'rgba(0, 0, 0, .7)'
            document.body.append(div)
          } else {
            document.body.removeChild(document.getElementById('loading'))
          }
        }
      })
      new Vue({
        el: '#root',
        data() {
          return {
            isLoading: false,
            data: ''
          }
        },
        methods: {
          update() {
            this.isLoading = true
            setTimeout(() => {
              this.data = '用户数据'
              this.isLoading = false
            }, 3000)
          }
        }
      })
    </script>
  </body>
</html>